(57) Modulation of microRNAs against myotonic dystrophy type 1 and antagonists of microRNAs therefor. The invention provides the use of inhibitors of microRNAs repressors of MBNL1 and/or MBNL2 genes for the manufacture of a medicinal product for the treatment of myotonic dystrophy 1. Inhibiting these microRNAs allows to increase the endogenous levels of the corresponding proteins MBNL1 and/or MBNL2, thereby alleviating symptoms of the disease, especially when inhibiting repressors that are expressed in the main affected organs: skeletal muscle, heart or organs of the central nervous system. The inhibition of the microRNAs miR-23b-3p and miR-218-5p is preferred. It also provides oligoribonucleotide or oligoribonucleotide analogue antagonists suitable therefor, preferably antagomiRs directed against the microRNAs mentioned with chemical modifications that enhance their interaction with the target, their stability in vivo and their ability to penetrate into the cells and distribute throughout tissues and organs.